code: def _maxout(x, pool_size, axis):
      shape = (
          x.shape[:axis]
          + (x.shape[axis] // pool_size, pool_size)
          + x.shape[axis + 1 :]
      )
      x = x.reshape(shape)
      return x.max(axis=axis + 1)
  
file_path: chainer/tests/chainer_tests/functions_tests/activation_tests/test_maxout.py
imports: import unittest
  import numpy
  import chainer
  from chainer import functions
  from chainer import testing
  from chainer.testing import attr
  from chainer.utils import type_check
label_desc: Use image node_id 1 for calling a global function with example usage: _maxout(x, pool_size, axis) and returns: x